Vehicle transmission systems, cooling systems, and braking systems may employ clutches or like devices to selectively transmit rotational forces from a drive source to an output member. For example, some cooling systems employ fan clutches that control the output rotation of engine cooling fans. Such a fan clutch can be driven by a drive pulley that rotates in response to the vehicle engine.
In general, the clutch can be operated to engage (or disengage) opposing clutch surfaces, which rotationally interconnect (or rotationally disconnect) the drive pulley and the output member. In an example related to fan clutches, when the clutch is shifted to the engaged position, friction surfaces engage and the output member (carrying fan blades) is driven to rotate along with the drive pulley. Over time, the friction surface can become worn, requiring replacement.
In some cases, the fan clutch in a vehicle can become inoperable due to wearing of the friction surfaces. For example, in some conventional fan clutch devices, a friction clutch ring is unable to engage an opposing friction surface when the friction clutch ring is worn below a threshold thickness. Accordingly, the fan clutch device is unable to force engagement of the friction surfaces and the fan blades are not driven to rotate (e.g., no cooling airflow is provided). Due to the lack of cooling airflow, the vehicle's engine may overheat or otherwise become highly inefficient.
These conventional fan clutch devices are typically supplied with a set of “come home” bolts for separate storage by the vehicle operator (e.g., placement in the vehicle cabin for use at a much later time. Thus, after a period of years when the friction ring of the fan clutch device is worn down below a threshold level so that the friction surfaces are no longer able to engage, the vehicle operator must attempt to locate the “come home” bolts that were stored years earlier. If the “come home” bolts are located, the vehicle operator must then attempt to install the bolts to the fan clutch device in the engine compartment. In general, the “come home” bolts are installed onto the outer periphery of the clutch device so as to temporarily bolt the output member to the input member, thereby causing permanent rotation of the fan blades until the vehicle can be driven to a repair facility. For vehicles such as large semi trucks or buses, the installation of the “come home” bolts may occur on the side of the road if the fan clutch fails during a long journey.